Role of central ANG II receptors in stress-induced cardiovascular and hyperthermic responses in rats.

The present study was carried out using a biotelemetry system to investigate whether central angiotensin II (ANG II) is involved in stress-induced cardiovascular and body temperature responses in rats. Intracerebroventricular injections of the nonselective ANG II-receptor antagonist saralasin and of the ANG II AT1-receptor antagonist losartan attenuated both the heart rate and pressor responses to immobilization stress in a dose-dependent manner. The elevation of plasma norepinephrine and epinephrine induced by immobilization stress was also suppressed by central ANG II-receptor blockade, suggesting a general attenuation of stress-induced sympathetic nervous and adrenomedullary activity by central ANG II-receptor blockade. The hyperthermia induced by immobilization stress was attenuated by central ANG II AT1-receptor blockade in a dose-dependent manner. The effects of central saralasin on the blood pressure response induced by immobilization stress were greater in Wistar-Kyoto rats than in spontaneously hypertensive rats. The present results suggest that central ANG II AT1-receptors are involved in expression of the tachycardia and hyperthermia, as well as the pressor response, induced by immobilization stress.